a 24-26mm synth (or two) is a good starting point, anything from PAA, RR, Yaqi. There are differences between knots, you can find many threads about it. I.e. plissoft, cashmere, synbad, etc are very soft with 0 backbone, tuxedo bit less soft, but more backbone. omega evo, simpson and mühle have higher end synths. I'd start with the cheaper ones, you'll be surprised how good they are. Get a boar from Omega or Zenith too. Excellent brushes for little money, but they need braking in. (anywhere between 10 and 50 shaves.)
After all this, if you still want to, get into badgers, but bring your wallet, especially if you want a big name, like Simpson.
Synths make great lather in no time with no effort. They use much less product than any natural hair brush. The only quality they lack behind is "face feel" and splaying them might feel unnatural compared to natural hair brushes (no surprise). They require a different technique than natural hair brushes.
After all this, if you still want to, get into badgers, but bring your wallet, especially if you want a big name, like Simpson.
Synths make great lather in no time with no effort. They use much less product than any natural hair brush. The only quality they lack behind is "face feel" and splaying them might feel unnatural compared to natural hair brushes (no surprise). They require a different technique than natural hair brushes.